A Democratic sweep is a realistic possibility, conservative scholar says

With Donald Trump down in the polls and openly feuding with some members of the Republican Party, there is a "realistic possibility" the Democrats will sweep the White House, Senate and House of Representatives this election, said Jimmy Pethokoukis, a scholar at the American Enterprise Institute.

"If you are worried about political risk in 2017 and 2018, I think you need to take this into account," he told CNBC's "Closing Bell" Wednesday.

The latest NBC/Wall Street Journalpoll released Tuesday shows Democratic nominee Hillary Clinton with 46 percent of support from likely voters in a four-way race, compared with 37 percent for Trump.

Jim Young | Reuters

Democratic presidential nominee Hillary Clinton and her vice presidential running mate Senator Tim Kaine celebrate among balloons after she accepted the nomination on the fourth and final night at the Democratic National Convention in Philadelphia, July 28, 2016.

The GOP nominee has also lashed out at Republicans he claims have been "disloyal." House Speaker Paul Ryan has said he would no longer defend Trump in the wake of a 2005 video showing Trump bragging about groping women. Other big-name Republicans have also announced they were withdrawing their support.

While Trump's troubles could pull support away from other Republican candidates, voters may also opt to pull the lever for Trump and ignore those who are not supporting him, said Pethokoukis, who is also a CNBC contributor.

Now Democrats "are talking about a clean sweep and being able to re-run the first term of Obama the way they would have liked to have done if it wasn't overshadowed by the financial crisis," he said.

That means things like the return of cap and trade, which is geared toward controlling greenhouse gas emissions, executive pay reform, paid leave and the Pacific Trade Deal, he noted.

He also thinks it may mean reforms in Obamacare and perhaps spending more money on it, as well as Clinton's tax hikes going through.